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diff --git a/sag-0.6.1-www/sag-0.6.1.html/x801.html b/sag-0.6.1-www/sag-0.6.1.html/x801.html new file mode 100644 index 0000000..e8d51b7 --- /dev/null +++ b/sag-0.6.1-www/sag-0.6.1.html/x801.html @@ -0,0 +1,218 @@ +<!DOCTYPE HTML PUBLIC "-//Norman Walsh//DTD DocBook HTML 1.0//EN"> +<HTML +><HEAD +><TITLE +>CD-ROM's</TITLE +><META +NAME="GENERATOR" +CONTENT="Modular DocBook HTML Stylesheet"><LINK +REL="HOME" +TITLE="The Linux System Administrators' Guide" +HREF="book1.html"><LINK +REL="UP" +TITLE="Using Disks and Other Storage Media" +HREF="c701.html"><LINK +REL="PREVIOUS" +TITLE="Floppies" +HREF="x787.html"><LINK +REL="NEXT" +TITLE="Tapes" +HREF="x811.html"></HEAD +><BODY +BGCOLOR="#FFFFFF" +TEXT="#000000" +><DIV +CLASS="NAVHEADER" +><TABLE +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TH +COLSPAN="3" +ALIGN="center" +>The Linux System Administrators' Guide</TH +></TR +><TR +><TD +WIDTH="10%" +ALIGN="left" +VALIGN="bottom" +><A +HREF="x787.html" +>Prev</A +></TD +><TD +WIDTH="80%" +ALIGN="center" +VALIGN="bottom" +>Chapter 4. Using Disks and Other Storage Media</TD +><TD +WIDTH="10%" +ALIGN="right" +VALIGN="bottom" +><A +HREF="x811.html" +>Next</A +></TD +></TR +></TABLE +><HR +ALIGN="LEFT" +WIDTH="100%"></DIV +><DIV +CLASS="SECT1" +><H1 +CLASS="SECT1" +><A +NAME="AEN801" +>CD-ROM's</A +></H1 +><P +>A CD-ROM drive uses an optically read, plastic coated disk. + The information is recorded on the surface of the + disk + + <A +NAME="AEN804" +HREF="#FTN.AEN804" +>[1]</A +> + + in small `holes' aligned along a spiral from the center to the + edge. The drive directs a laser beam along the spiral to read + the disk. When the laser hits a hole, the laser is reflected in + one way; when it hits smooth surface, it is reflected in another + way. This makes it easy to code bits, and therefore information. + The rest is easy, mere mechanics.</P +><P +>CD-ROM drives are slow compared to hard disks. Whereas a + typical hard disk will have an average seek time less than + 15 milliseconds, a fast CD-ROM drive can use tenths of a second + for seeks. The actual data transfer rate is fairly high at + hundreds of kilobytes per second. The slowness means that + CD-ROM drives are not as pleasant to use instead of hard disks + (some Linux distributions provide `live' filesystems on CD-ROM's, + making it unnecessary to copy the files to the hard disk, making + installation easier and saving a lot of hard disk space), although + it is still possible. For installing new software, CD-ROM's are + very good, since it maximum speed is not essential during + installation.</P +><P +>There are several ways to arrange data on a CD-ROM. The most + popular one is specified by the international standard ISO 9660. + This standard specifies a very minimal filesystem, which is + even more crude than the one MS-DOS uses. On the other hand, + it is so minimal that every operating system should be able to + map it to its native system.</P +><P +>For normal UNIX use, the ISO 9660 filesystem is not usable, so + an extension to the standard has been developed, called + the Rock Ridge extension. Rock Ridge allows longer filenames, + symbolic links, and a lot of other goodies, making a CD-ROM + look more or less like any contemporary UNIX filesystem. + Even better, a Rock Ridge filesystem is still a valid ISO 9660 + filesystem, making it usable by non-UNIX systems as well. + Linux supports both ISO 9660 and the Rock Ridge extensions; + the extensions are recognized and used automatically.</P +><P +>The filesystem is only half the battle, however. Most CD-ROM's + contain data that requires a special program to access, and + most of these programs do not run under Linux (except, possibly, + under dosemu, the Linux MS-DOS emulator).</P +><P +>A CD-ROM drive is accessed via the corresponding device file. + There are several ways to connect a CD-ROM drive to the computer: + via SCSI, via a sound card, or via EIDE. The hardware hacking + needed to do this is outside the scope of this book, but the + type of connection decides the device file. See XXX (device-list) + for enlightment.</P +></DIV +><H3 +>Notes</H3 +><TABLE +BORDER="0" +CLASS="FOOTNOTES" +WIDTH="100%" +><TR +><TD +ALIGN="LEFT" +VALIGN="TOP" +WIDTH="5%" +><A +NAME="FTN.AEN804" +HREF="x801.html#AEN804" +>[1]</A +></TD +><TD +ALIGN="LEFT" +VALIGN="TOP" +WIDTH="95%" +><P +>That is, the surface inside + the disk, on the metal disk inside the plastic + coating.</P +></TD +></TR +></TABLE +><DIV +CLASS="NAVFOOTER" +><HR +ALIGN="LEFT" +WIDTH="100%"><TABLE +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +><A +HREF="x787.html" +>Prev</A +></TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +><A +HREF="book1.html" +>Home</A +></TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +><A +HREF="x811.html" +>Next</A +></TD +></TR +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +>Floppies</TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +><A +HREF="c701.html" +>Up</A +></TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +>Tapes</TD +></TR +></TABLE +></DIV +></BODY +></HTML +>
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